SQL Wrap: Practice Tips + Mistakes to Avoid

How to practice smart, debug faster, and interview with clarity.

Welcome to Zero2DataEngineer — Day 5 of SQL Week

You made it.
Through SELECTs, WHEREs, JOIN explosions, and LAG - induced enlightenment.

This final SQL lesson isn’t about more syntax.
It’s about how to practice like a Data Engineer — so you can solve real-world problems, not just pass quizzes.

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Practice Like a Data Engineer, Not a LeetCode Addict

Most people keep solving the same "top 3 products" problem over and over.

Here’s how to actually practice:

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Reuse Patterns — Not Just Syntax

Here are 3 DE-approved SQL templates I reuse constantly:

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ROW_NUMBER De-Dupe Template

WITH ranked_data AS (
  SELECT *, ROW_NUMBER() OVER (
    PARTITION BY user_id
    ORDER BY updated_at DESC
  ) AS rn
  FROM users
)
SELECT * FROM ranked_data
WHERE rn = 1;